Two-dimensional transition metal dichalcogenide materials, such as the heterobilayers by piling up the monolayers in out-of-plane direction, behave unique performances in applications of nanoelectronic components. In this work, the in-plane thermal conductivities of MoS2–MoSe2, MoS2–WS2, and MoS2–WSe2 heterobilayers are investigated with nonequilibrium molecular dynamics method by considering the effects of system dimensions, temperature, coupling strength, strain, and misorientation. The results show that the thermal conductivity decreases as the temperature rises from 100 K to 500 K. The effect of coupling strength on the thermal conductivity is not significant. Both strain and misorientation could result in a reduction in the thermal conductivity, and the effect of tensile strain is stronger than that of compressive strain. An analysis based on phonon spectral energy density is performed to further understand phonon thermal properties in heterobilayers. This work provides a fundamental basis for regulating thermal transport in two-dimensional heterobilayer-based nanoelectronics.

Low-dimensional materials have an excellent prospect in thermoelectric applications. We have investigated the geometric structure, band structure, and electron transport properties of hydrogenated and pure multilayer silicene using first-principle calculation within density functional theory. The Boltzmann theory for electrons under relaxation time approximation was employed to obtain the Seebeck coefficient and electrical conductivity. The calculations of electron relaxation time were based on the deformation potential theory. Hydrogenation can effectively change the band structure of multilayer silicene. The simulation results reveal a big difference in the relaxation times between pure and hydrogenated structures. And, this difference decreases as the layer number n increases. The anisotropy of hydrogenated structures leads to a high thermoelectric performance along the armchair direction. When the layer number n is larger than 2, hydrogenation can greatly improve the electronic figure of merit ZT(e) of multilayer silicene. The band structure can also be engineered by adjusting the hydrogenation ratio. A band of 0.33 eV can be achieved when the hydrogenation ratio is 66.7%. By combining the adjustment of the hydrogenation ratio with the method of changing the geometric structure, a high thermoelectric performance can be achieved in multilayer silicene. The results provide a viable strategy for thermoelectric optimization in multilayer silicene, and can be potentially extended to the thermoelectric optimization of other two-dimensional materials.

A ferromagnetic transition is generally regardedas a diffusionless process, exhibiting a sharpchange of magnetic properties with temperature. In this paper, however, we report a ferromagnetic diffuse phase transition (FDPT) induced by Griffiths phase in La1-xSrxMnO3 (0.06 <= x <= 0.2). Such a FDPT experiences a broad transition temperature range, resulting in temperature-controlled ferromagnetic cluster owing to the existence of Griffiths phase during the diffusion process. The transition temperature range calculated from M-T curve is as large as 146 K for the FDPT sample. Further analysis suggests that this novel FDPT has the same scenario with that in the ferroelectric relaxor, where the ferroelectric clusters are embedded in the paraelectric matrix.

The phonon Boltzmann transport equation with the frequency-dependent model is solved numerically to study the thermal conductivity in nanoporous thin film and nanocomposite. Local angle between heat fluxes, defined as the angle between the directions of heat flux component qx and the local heat flux q, is introduced. At a fixed porosity or interface area, the thermal conductivity, local angle distribution, and the average angle of the two-dimensional nanoporous thin films with circular, hexagonal, square, and triangular pores are reported, and the thermal conductivity decreases with the increase in the interface area or porosity. Furthermore, the relationship between the thermal conductivity and average angle is also discussed for the three-dimensional nanoporous thin films with aligned or staggered pores, and silicon-germanium embedded and compacted nanocomposites. All the results show that the nanostructured material with a larger average angle between heat fluxes has a lower thermal conductivity.

We fabricated CoFe2O4 (CFO) nanofibers (NFs) and nanoparticles (NPs) via electrospinning and the conventional sol–gel process, respectively. Sizes of these nanomaterials can be controlled by adjusting the annealing temperature. Magnetic dynamic behaviour showed differences between them. These differences have been linked to specific size and shape configurations. At room temperature, magnetic properties were size dependent, but the specific shape configuration dominated the magnetic properties at 5 K.

Controlling the thermal conductivity of thermoelectric materials continues to be a goal for energy conversion applications. The Phonon Boltzmann Transport Equation is solved by using the Discrete Ordinates Method to numerically study the phonon thermal conductivity of nano-structured silicon thin film with pores in this study. The effects of the film thickness, film porosity, and porous structure are concerned. The numerical results show that the nano-pores are able to reduce the thermal conductivity of the silicon thin film sharply by the phonon boundary scattering, and the scattering boundary area has significant effect on the thermal conductivity. The method of local angle distribution between heat fluxes is introduced for the first time to optimize the pore placement for reducing the thermal conductivity.